remove php gd dependency

Image error messages were shown using PHP GD. People who haven't installed
PHP GD don't understand what is going on when an image is not shown. It is
replaced by a static image referring to the error log for more information.

4 files changed, 10 insertions, 16 deletions

diff --git a/graph.php b/graph.php
index effecef..e170598 100644
--- a/graph.php
+++ b/graph.php
@@ -8,29 +8,17 @@ $width = empty($_GET['x']) ? $CONFIG['width'] : $_GET['x'];
 $heigth = empty($_GET['y']) ? $CONFIG['heigth'] : $_GET['y'];
 
 if (validate_get($_GET['h'], 'host') === NULL) {
-        die_img('Error: plugin contains unknown characters.');
-        exit;
+        error_log('CGP Error: plugin contains unknown characters');
+        error_image();
 }
 
 if (!file_exists($CONFIG['webdir'].'/plugin/'.$plugin.'.php')) {
-        die_img(sprintf('Error: plugin not available (%s).', $plugin));
-        exit;
+        error_log(sprintf('CGP Error: plugin "%s" is not available', $plugin));
+        error_image();
 }
 
 # load plugin
 include $CONFIG['webdir'].'/plugin/'.$plugin.'.php';
 
 
-function die_img($msg) {
-        header("Content-Type: image/png");
-        $image = ImageCreatetruecolor(300, 30);
-        $black = ImageColorAllocate($image, 0, 0, 0);
-        $white = ImageColorAllocate($image, 255, 255, 255);
-        imagefill($image, 0, 0, $white);
-        imagerectangle($image, 0, 0, 299, 29, $black);
-        imagestring($image, 2, 10, 9, $msg, $black);
-        imagepng($image);
-        imagedestroy($image);
-}
-
 ?>
diff --git a/inc/functions.inc.php b/inc/functions.inc.php
index b0706d5..04e58e3 100644
--- a/inc/functions.inc.php
+++ b/inc/functions.inc.php
@@ -27,4 +27,10 @@ function crc32hex($str) {
         return sprintf("%x",crc32($str));
 }
 
+function error_image() {
+        header("Content-Type: image/png");
+        readfile('layout/error.png');
+        exit;
+}
+
 ?>
diff --git a/layout/error.png b/layout/error.png
new file mode 100644
index 0000000..421fbfe
--- /dev/null
+++ b/layout/error.png
diff --git a/layout/error.xcf b/layout/error.xcf
new file mode 100644
index 0000000..4ff54e3
--- /dev/null
+++ b/layout/error.xcf